Les profils de composition en oligoelements des pollens, marqueurs potentiels en cladistique vegetale

In botany tentative attempts have been made to classify species, based not on the plant as a whole, but on a particular character, for example pollen characteristics. Pollen, which is involved in the transmission of male genetic information during sexual reproduction, is of particular interest in distinguishing plants and their relationships.These characters, observed in photon- and scanning electron- microscopy are symmetry, form, number and position of germinating areas. Being genetically stable for a given species, they identify a plant.Recently, a novel character has been added: the concentration of elements in the exine, determined by electron probe micro-X-ray analysis. It is interesting to follow relationship of plant species, based on the mineral composition of their pollen as a whole, taking into account both plastic and oligoelements, obtained via an inductive coupled plasma spectrometer. Samples of pollen from different plant species, at distinct taxonomic levels, were analyzed; the results were submitted to a normalisation procedure and the standard patterns obtained were investigated by means of a number of numerical techniques (clustering and factor analysis). The aim was to establish if elements could be considered as chemical markers in plant cladistics. The mineral composition in a given species appeared quite stable and this furnished a convenient identification-critorion.This approach further allows a chemo-taxonomy of species, in as much as organization of families, and perhaps orders, would conform to the phylogenetic proximity-criterion. Hence, we found clusters including pollen of Gramineae, Coniferae, Betulaceae…This methodology, that should be completed and corroborated on a wider range of samples would provide an original responsee to the problems of identification and classification encountered in a pollen bank. It follows that:Hence, the working hypothesis that the chemical markers and, in particular, oligo-elements, complete pollen typologies based on morphological and structural characters, appears quite reasonable.In conclusion, this paper brings a complement to the mineral composition of the exine.En botanique, des tentatives ont ete faites pour classer les especes non plus a partir d'individus pris dans leur integralite, mais sur la base d'une de leurs particularites, par exemple a partir des caracteristiques offertes par les pollens. Ainsi, le pollen, dont le role est de transmettre l'information genetique male de la plante au moment de la reproduction sexuee, presente des caracteres de premier ordre utilisables pour distinguer les differentes plantes et pour situer leur parente et leur filiation.Ces caracteres, que l'on observe en microscopies photonique et electronique a balayage sont la symetrie, la forme, le nombre et la position des zones germinatives. Pour une espece genetiquement stable, ils constituent la carte d'identite de la plante.Il est interessant de continuer a explorer la voie de la structuration des especes vegetales basee sur la connaissance chimique du pollen en determinant sa composition en oligo-elements par l'utilisation d'un spectrometre a plasma a couplage inductif. Ainsi, des echantillons de pollens appartenant a diverses especes vegetales situees a differents niveaux taxinomiques ont ete analyses et les resultats normalises sous forme de profils standard ont ete soumis a differentes techniques d'analyse statistique mathematique (classification automatique et analyse factorielle). Le but de cette approche est d'apprecier l'aptitude des elements mineraux a etre des marqueurs chimiques en cladistique vegetale.Les resultats obtenus ont permis de constater la relative stabilite du profil en composition minerale au sein d'une meme espece vegetale, ce qui donne acces a un critere d'identification commode.Cette approche permet d'autre part une chimiotaxinomie des plantes etudiees.Cette approche methodologique semble susceptible d'apporter une reponse originale aux problemes de conservation. Les pollens conserves doivent avoir la meme composition minerale que les pollens frais.— the pattern of pollen composition of oligo-elements, calcium and magnesium is a marker in plant cladistics. Since a typology depending on proximity is found between plant species, families and orders.— an unknown pollen sample may be located, tentatively, on the base of a described model of pollen relation (shortest connexion network — Prim algorithm — and pollen of Bactris-oil palm and Phoenix dactylifera).